This invention is concerned with the extraction of bitumen from tar sands.
Approximately 30 billion barrels of tar sand bitumen in Athabasca (out of 625 billion barrels in Alberta) and part of 26 billion barrels in Utah are accessible to mining. The mined sands are now commercially processed for bitumen recovery by the "Clark Hot Water" method. In the Athabasca region, it has been estimated that, at most, two additional plants of the 125,000 bpd size can make use of this recovery technique; this restriction stems from severe environmental constraints such as high water and energy consumption and tailings disposal. Two alternate bitumen recovery methods are being pursued: thermal treatment (e.g., retorting) and extraction with solvents. Both have high energy requirements; the first--poor sensible heat recovery and the burning of part of the resources, and the second--solvent-bitumen separation and solvent loss through incomplete steam stripping. Shortcomings of these approaches are minimized by the present process. Finally, Utah tar sand and mineable resources in the Athabasca region are both recoverable by this method.